Method of fabricating large area cathode

ABSTRACT

Pairs of cathode side rods are positioned in grooves on opposite sides of a shaped winding mandrel. Electron emissive material coated cathode wire is helically wound about the mandrel and over the side rods. After winding, the electron emissive material that directly overlies the cathode side rods is removed and a similar shaped side rod is then welded thereover which fixes the wires between the two side rods. Thereupon, the cathode windings are cut in the area between an upper and lower side rod thus forming two individual large area cathodes. The novel winding mandrel comprises a shaped body with suitable grooves provided therein for receiving the cathode side rods.

United States Patent Smithgall 5] Nov. 25, 1975 [54] METHOD OF FABRICATING LARGE AREA 3,600,778 8/1971 Martin 29/2s.14 CATHODE 3,780,928 12/1973 Shim 81/951 Inventor: Harry E. Smithgall, Seneca Falls,

GTE Sylvania Incorporated, Stamford, Conn.

Filed: July 15, 1974 Appl. No.: 488,534

Assignee:

US. Cl. 29/25.l4; 29/25.l7; 140/715; 313/346 R Int. Cl. H01] 9/02 Field of Search 29/25.l, 25.13, 25.14, 29/25.17, 25.15, 25.16; 140/922, 71.5, 71.6; 81/951; 313/346 R References Cited UNITED STATES PATENTS 10/1923 Trimble 29/25.l4

10/1933 Zimber 29/25.17

12/1955 Bongers 29/25.17

1/1958 Bahn 140/715 2/1960 Zoschg 81/951 Primary Examiner-Roy Lake Assistant ExaminerJames W. Davie Attorney, Agent, or Firm-Norman J. OMalley; William H. McNeill; Robert T. Orner [57] ABSTRACT Pairs of cathode side rods are positioned in grooves on opposite sides of a shaped winding mandrel. Electron emissive material coated cathode wire is helically wound about the mandrel and over the side rods. After winding, the electron emissive material that directly overlies the cathode side rods is removed and a similar shaped side rod is then welded thereover which fixes the wires between the two side rods. Thereupon, the cathode windings are cut :in the area between an upper and lower side rod thus forming two individual large area cathodes The novel winding mandrel comprises a shaped body with suitable grooves provided therein for receiving the cathode side rods.

3 Claims, 7 Drawing Figures US. Patent Nov. 25, 1975 Sheet 1 of2 3,921,269

Sheet 2 of 2 3,921,269

US. Patent Nov. 25, 1975 METHOD OF FABRICATING LARGE AREA CATHODE BACKGROUND OF THE INVENTION This invention relates to electron emitting cathodes and primarily to large area electron emitting cathodes. Such large area cathodes are a necessary and vital component in electron beam scanning devices of the type described in U.S. Pat. No. 3,539,719.

Prior attempts to formulate large area cathodes have been largely unsuccessful. These prior attempts have attempted to use existing cathode technology and have run into many problems. For example, one of the first attempts was to sinter a tungsten heater wire to a large nickel sheet and then coat the sheet with a cathode material. This attempt was doomed to failure because of the differences in the coefficient of expansion between the nickel and the tungsten. When operated for any length of time, it was found that the cathode bowed and warped.

Another attempt that has been utilized has been to put heater wires into corrugated receptacles spot welded to one side of a nickel sheet. The opposite side of the nickel sheet was then coated with an emissive material. This attempt also proved unsuccessful because excessive heat was developed and excessive current was drawn.

Still other attempts have been utilized which comprised using individual directly heated. cathode wires. These filament wires were welded individually between spaced tensioning springs. This approach has been found to be disadvantageous because of its attendant hand operation and the nonuniformities that result. Furthermore, the low production rate and high cost are not conducive to a suitable cathod operation.

' OBJECTS AND SUMMARY OF THE INVENTION It is therefor an object of this invention to obviate the disadvantages of the prior art.

It is yet another object of the invention to provide a simple and economical method of fabricating large area cathodes.

Yet another object of the invention is the provision of a method of simultaneously making at least two large area cathodes.

These objects are accomplished in one aspect of the invention by the provision of a method for fabricating at least two large area cathodes simultaneously. The method comprises positioning a winding mandrel at a winding station. The mandrel is formed from suitable material and comprises body having upper and lower surfaces each of which is provided with a pair of spaced apart grooves. Pairs of electrically conductive cathode side rods are positioned in the grooves. Thereafter a cathode wire coated with electron emissive material is helically wound around the mandrel and over the cathode side rods. At the completion of the winding operation, the electron emissive material is removed from the cathode wire in those areas where it immediately overlies the side rods. Thereafter. each turn of wire now in contact with the side rod is fixed thereto. The wires are then severed at points between an upper and lower side rod at each side of the mandrel to form at least two area cathodes.

It will be seen from the above description that there is herein provided a unique and novel method for rapidly and efficiently providing large area cathodes at an extremely economical cost. The cathodes are produced at least two at a time which still further provides increased operating efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a winding mandrel utilized with the invention;

FIG. 2 is a diagrammatic illustration of the first por: tion of the winding operation;

FIG. 3 is a similar view at the completion of the winding operation;

FIG. 4 illustrates diagrammatically a means of removing the electron emissive material from appropriate sections of the coated wire;

FIG. 5 illustrates the method of separating the two previously formed cathodes;

FIG. 6 is an enlarged sectional view of the step of attaching the wires to the side rods; and

FIG. 7 is a perspective view of a finished cathode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above described drawings.

Referring now to the drawings with greater particularity, there is shown in FIG. 1 a winding mandrel 10 for use in fabricating at least two area cathodes simultaneously. The mandrel 10 comprises a substantially rectangular body l2 formed from a suitable material such as steel. The body 12 is provided with upper and lower opposed surfaces 14 and I6 respectively. Each of the upper and lower surfaces is provided with a pair of spaced apart grooves 18 and 19 respectively, extending parallel to arcuately formed sides 20 and 21 which connect the upper and lower surfaces. In the particular embodiment shown, the pairs of grooves I8 and 19 are oppositely disposed from one another, and in this case cathodes formed thereon would be of identical size. However, if it should be desired to use a single winding mandrel to fabricate two different sized cathodes simultaneously. then the grooves on either the upper or lower surface could have a substantially different spac ing than the grooves on the other surface. To save material and reduce the weight of the mandrel the central portions 22 thereof can be cut out. The use of the above described mandrel in the cathode fabricating process will be described in connection with FIGS 2-5. Referring now to FIG. 2. it will be seen that the mandrel 10 is positioned at a winding station. Pairs of electrically conductive cathode side rods 24 and 26 respectively are positioned in grooves 18 and 19 respectively. A cathode wire 27 coated with. electron emissive material is drawn from a supply 30 which can be a spool of suitable coated wire, and the end portion thereof is fixed to one of the cathode side rods 24. The end of the cathode wire 28 can be affixed to the cathode side rod 24 by any suitable mean s, such as welding. Upon affixation of the end of the wire 28 to a side rod 24, relative rotational movement is caused to occur between the mandrel I0 and the wire supply 30 together with sufficient longitudinal movement of the mandrel 10 to helically wind the cathode wire 27 about the mandrel l0 and over the pairs of side rods 24 and 26. At the completion of the winding the mandrel and wound wire will look approximately as in FIG. 3.

Upon termination of the winding, the cathode wire 27 is severed from the remainder of the wire supply 30 and is also affixed to one of the cathode side rods by any suitable means.

Referring now to FIG. 4. the next step in the operation will be the removal of some of the electron emissive material from the cathode wire 27 at those places where the wire overlies the pairs of side rods 24 and 26. In the embodiment shown in FIG. 4, this is accomplished by a crushing operation provided by rollers 32 being moved over the wires 27 where they cross pairs of side rods 24 and 26. Air nozzles 34 can be employed to remove the crushed emissive material. After the removal of the crushed electron emissive material, the wire is affixed to the pairs of cathode side rods 24, 26 by any suitable means. such as welding.

In the embodiment shown in FIG. 5. the affixation is accomplished by placing over the pairs of side rods 24 and 26 substantially similar pairs of side rods 24' and 26 and welding the two side rods together throughout their entire length. FIG. 6 depicts this operation in enlarged detail. Thereafter, cutting tools 35 are employed to sever the wires at points between the upper and lower side rods. which operation forms two complete cathode assemblies.

Each of the cathodes thus prepared can be mounted to a suitable assembly 32 (FIG. 7) by fixing either of the pairs of side rods (24 or 24, for example) to substantially L-shaped springs 36 by any suitable means. such as welding. The L-shaped springs 36 can then be affixed to any suitable mounting means shown. in this particular instance as channel members 40, 42.

This assembly can then be mounted in an electron beam scanning device for suitable operation therewith.

It will be seen from the above that there is herein provided a new and unique method of fabricating large area cathodes. While the disclosure above has described a process whereby two cathodes are simultaneously formed, it will be apparent that a larger number of cathodes could be fabricated simultaneously by extending the length of the mandrel 10. In other words. extremely long cathode assemblies could be wound and then separated into appropriate sizes by shearing longitudinally.

While there have been shown what are at present considered to be the preferred embodiments of the invention. it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

I. In a method of fabricating at least two area cathodes simultaneously, the steps of: positioning a mandrel at a winding station, said mandrel having opposed upper and lower surfaces each being provided with a pair of spaced apart grooves; positioning pairs of electrically conductive cathode side rods in said grooves; helically winding a cathode wire coated with electron emissive material around said mandrel and over said cathode side rods; removing said electron emissive material from said cathode wire where it overlies said side rods; fixing each turn of said wire to said side rods; and severing said wires at points between said upper and lower side rods to form at least two area cathodes.

2. The method of claim I wherein said electron emissive material is removed by crushing.

3. The method of claim 2 wherein said wires are fixed to said side rods by welding to said side rods similarly shaped side rods. 

1. In a method of fabricating at least two area cathodes simultaneously, the steps of: positioning a mandrel at a winding station, said mandrel having opposed upper and lower surfaces each being provided with a pair of spaced apart grooves; positioning pairs of electrically conductive cathode side rods in said grooves; helically winding a cathode wire coated with electron emissive material around said mandrel and over said cathode side rods; removing said electron emissive material from said cathode wire where it overlies said side rods; fixing each turn of said wire to said side rods; and severing said wires at points between said upper and lower side rods to form at least two area cathodes.
 2. The method of claim 1 wherein said electron emissive material is removed by crushing.
 3. The method of claim 2 wherein said wires are fixed to said side rods by welding to said side rods similarly shaped side rods. 